1. Field of the Invention:
The present invention relates generally to a self-pumping hydropneumatic strut with an internal level control, especially for automobiles. The self-pumping hydropneumatic strut has a power cylinder which is under the pressure of at least one gas pad acting as a spring. The gas pad is placed in a high-pressure chamber, which high-pressure chamber is filled with damping agents. The power cylinder is divided into two working chambers by a working piston. The working piston is carried by a hollow piston rod and is equipped with valves. A piston pump is driven by the spring motion and transports oil from a low-pressure chamber into the working chamber that is connected to the high-pressure chamber. The piston pump includes a pump chamber formed by the hollow piston rod and a pump rod that is connected to the power cylinder.
2. Background Information:
Self-pumping hydropneumatic struts are already known (e.g., German Patent No. 38 40 790 and German Patent No. 39 14 385, which corresponds to U.S. Pat. No. 5,062,616), where, by means of the piston pump of the strut, while the vehicle is in motion, damping agents are pumped into the power cylinder until the level position of the vehicle is reached. After reaching the level position, the power cylinder disengages a downward-control opening so that, with the aid of a short circuit or bypass, further upward-control of the vehicle's built-up can be avoided. In order to reach the level position while the vehicle is charging, immediately after starting the vehicle, it is possible, while the vehicle is not in motion, to transport oil into the working chamber by means of a pressurized accumulator. In contrast to the high-pressure chamber and the low-pressure chamber, the pressurized accumulator is impacted with higher pressure so that, when the vehicle is charging, the piston rod, in the standing position, dives into the strut, and thus a bypass system between the pressurized accumulator and the high-pressure chamber is opened. As a rule, the volume of the pressurized accumulator is sufficient for a one-time actuation so that during the next trip, by means of the piston pump, charging of the pressurized accumulator must once again take place.